Subsurface drilling tool

ABSTRACT

An improved subsurface drill bit includes two rotatable cutters disposed between two ear portions of a shank, each of the rotatable cutters having an arcuate face and cutting elements. Cutting edges of the cutting elements, outer surfaces of the ear portions, and protrusions extending outwardly from the shank collectively define a circular configuration to prevent backflow of drilling debris and to prevent wobble of the drill bit in operation. The two rotatable cutters can have an on-load configuration in which each of the cutters is in contact with each other, and an off-load configuration in which each of the cutters is in contact with one of the ear portions. Several improved rotatable cutters are provided. The rotatable cutters can be interchangeable. The drill bit can further include an improved fluid delivery system, including multiple fluid passageways and reverse jets.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of U.S. application Ser. No. 14/290,597, filed on May 29, 2014, which claims the benefit of U.S. Provisional Appl. No. 61/879,131, filed on Sep. 17, 2013; and a continuation-in-part application of U.S. application Ser. No. 14/465,907, filed on Aug. 22, 2014, which claims the benefit of U.S. application Ser. No. 14/290,597 and U.S. Provisional Appl. No. 61/879,131, all of which are incorporated by reference herein in their entireties.

FIELD OF THE DISCLOSURE

The present disclosure relates in general to subsurface drilling tools and cutting elements for drill bits or other tools incorporating the same. More specifically, embodiments disclosed herein relate generally to rotatable cutting elements for rotary drill bits for deep well drilling.

BACKGROUND OF THE DISCLOSURE

Drill bits used to drill wellbores through earth formations generally are made within one of two broad categories of bit structures. Depending on the application/formation to be drilled, the appropriate type of drill bit may be selected based on the cutting action type for the bit and its appropriateness for use in the particular formation. Drill bits in the category generally known as “roller cone” bits, include a bit body having one or more roller cones rotatably mounted to the bit body. The bit body is typically formed from steel or another high strength material. The roller cones are also typically formed from steel or other high strength material and include a plurality of cutting elements disposed at selected positions about the cones. The cutting elements may be formed from the same base material as is the cone. These bits are typically referred to as “milled tooth” bits. Other roller cone bits include “insert” cutting elements that are press (interference) fit into holes formed and/or machined into the roller cones. The inserts may be formed from, for example, tungsten carbide, natural or synthetic diamond, boron nitride, or any one or combination of hard or superhard materials.

Drill bits of the category typically referred to as “fixed cutter” or “drag” bits, include bits that have cutting elements attached to the bit body. Drag bits may generally be defined as bits that have no moving parts. However, there are different types and methods of forming drag bits that are known in the art. For example, drag bits having abrasive material, such as diamond, impregnated into the surface of the material which forms the bit body are commonly referred to as “impreg” bits. Drag bits having cutting elements made of an ultra-hard cutting surface layer or “table” (typically made of polycrystalline diamond material or polycrystalline boron nitride material) deposited onto or otherwise bonded to a substrate are known in the art as polycrystalline diamond compact (“PDC”) bits. PDC bits drill soft formations easily, but they are frequently used to drill moderately hard or abrasive formations. They cut rock formations with a shearing action using small cutters that do not penetrate deeply into the formation. Because the penetration depth is shallow, high rates of penetration are achieved through relatively high bit rotational velocities.

PDC cutters have been used in industrial applications including rock drilling and metal machining for many years. In PDC bits, PDC cutters are received within cutter pockets, which are formed within blades extending from a bit body, and are typically bonded to the blades by brazing to the inner surfaces of the cutter pockets. The PDC cutters are positioned along the leading edges of the bit body blades so that as the bit body is rotated, the PDC cutters engage and drill the earth formation. In use, high forces may be exerted on the PDC cutters, particularly in the forward-to-rear direction. Additionally, the bit and the PDC cutters may be subjected to substantial abrasive forces. In some instances, impact, vibration and erosive forces have caused drill bit failure due to loss of one or more cutters, or due to breakage of the blades.

In a typical PDC cutter, a compact of polycrystalline diamond (“PCD”) (or other superhard material, such as polycrystalline cubic boron nitride) is bonded to a substrate material, which is typically a sintered metal-carbide to form a cutting structure. PCD comprises a polycrystalline mass of diamond grains or crystals that are bonded together to form an integral, tough, high-strength mass or lattice. The resulting PCD structure produces enhanced properties of wear resistance and hardness, making PCD materials extremely useful in aggressive wear and cutting applications where high levels of wear resistance and hardness are desired.

A significant factor in determining the longevity of PDC cutters is the exposure of the cutter to heat. Conventional polycrystalline diamond is stable at temperatures of up to 700-750° Celsius in air, above which observed increases in temperature may result in permanent damage to and structural failure of polycrystalline diamond. This deterioration in polycrystalline diamond is due to the significant difference in the coefficient of thermal expansion of the binder material, cobalt, as compared to diamond. Upon heating of polycrystalline diamond, the cobalt and the diamond lattice will expand at different rates, which may cause cracks to form in the diamond lattice structure and result in deterioration of the polycrystalline diamond. Damage may also be due to graphite formation at diamond-diamond necks leading to loss of microstructural integrity and strength loss, at extremely high temperatures.

Exposure to heat (through brazing or through frictional heat generated from the contact of the cutter with the formation) can cause thermal damage to the diamond table and eventually result in the formation of cracks (due to differences in thermal expansion coefficients) which can lead to spalling of the polycrystalline diamond layer, delamination between the polycrystalline diamond and substrate, and conversion of the diamond back into graphite causing rapid abrasive wear. As a cutting element contacts the formation, a wear flat develops and frictional heat is induced. As the cutting element is continued to be used, the wear flat will increase in size and further induce frictional heat. The heat may build-up that may cause failure of the cutting element due to thermal miss-match between diamond and catalyst discussed above. This is particularly true for cutters that are immovably attached to the drill bit, as conventional in the art. Accordingly, there exists a continuing need to develop ways to extend the life of a cutting element and improve the drilling process.

Debris associated with the drilling process are removed through the well with the use of fluids. In particular, fluid is pumped through a drill string and drill bit to not only lubricate the cutting area, but also urge debris upwardly outside of the drilling string. As the depth of the wellbore increases, the amount of debris and the hydrostatic pressure of the fluid increase. In fact, sufficient backpressure created by the debris and fluid can effectively exceed the pressure provided to the wellbore by a pump, causing a “reversal” of the fluid delivery system. Further, the greater the clearance between the drill bit and the drill bore provides for greater backpressure, as the fluid and debris will occupy greater volume at any particular depth. Therefore, a need exists in the art for a drill bit with an improved profile to minimize clearance between the bit and the drill bore and improve the efficiency of debris removal.

Directional drilling is well developed in the art. Among other things, directional drilling permits the drill bore to be vertical, angled, or even horizontal. While drilling on an angle, and especially horizontal, the drill bit can wobble within the drill bore. This can be caused by, among other things, the drilling end of the drill bit having a wider profile than the pin end closest to the drill string. The wobble can decrease drilling efficiency and increase wear on the shank of the drill bit. Therefore, a need exists in the art for a drill bit configured to minimize and/or prevent wobble within the wellbore.

In addition to typical wellbore drilling, an additional application of particular interest is cased-hole drilling. In cased-hole drilling, casing strings comprised of elongated tubular members are inserted into a borehole and cemented in place. The casing provides several advantages, including providing a smooth internal bore, preventing fluid loss, preventing contamination of fresh water well zones, and permitting zonal isolation. To isolate zones of different pressures or fluids, bridge plugs are commonly used to hydraulically isolate respective zones. For example, during fracturing of a well, a zone of interest should be hydraulically isolated from a lower pressure zone.

During the completion process of a well, bridge plugs, including composite bridge plugs, need to be removed from the well casing. Removal of the bridge plugs are associated with several technological shortcomings. One preferred method of removing bridge plugs is through milling as described in U.S. Pat. No. 8,127,851 to Misselbrook, which is herein incorporated by reference in its entirety. However, bridge plugs are often constructed from brittle metals such as cast iron, which is not particularly conducive to milling. The milling of the plugs can result in undesirably large chunks of the plug, which can become lodged in the lateral of the casing. Further, milling produces undesirably high levels of torque. Another method of removing bridge plugs is through drilling with a tri-cone bit. In addition to not being designed for the application, the tri-cone drill bit can mechanically fail, after which one of the three cones may become lodged in the wellbore. The speed with which the motor can drive the tri-cone bit and the weight that can be applied to the bit is limited due to the use of ball bearings in a tri-cone bit. Therefore, a further need exists in the art for an improved drill bit capable of more effectively removing bridge plugs.

BRIEF SUMMARY OF THE DISCLOSURE

Therefore, it is a principal object, feature, and/or advantage of the present disclosure to overcome the aforementioned deficiencies in the art and provide a new and improved subsurface drilling tool that will efficiently drill hard rock formations.

It is another object, feature, and/or advantage of the present disclosure to provide a subsurface drilling bit with new and improved alternating rotating cones having hard inserts embedded therein and protruding therefrom to crush hard rock formation.

It is still another object, feature, and/or advantage of the present disclosure to provide a subsurface drilling bit that eliminates or minimizes sticky clay or shale drill cuttings from preferentially adhering to and “balling-up” a drill bit cutting face while drilling in a borehole.

It is yet another object, feature, and/or advantage of the present disclosure to provide a subsurface drilling bit that has replaceable hard inserts embedded therein for easy access and increased efficiency.

It is another object, feature, and/or advantage of the present disclosure to drill in three dimensions to shear, puncture, pulverize, twist and chisel both rock formation and bridge plugs in cased-well drilling. An exemplary drill bit of the present disclosure can degrade bridge plugs into pieces of approximately one-eighth inch or less to more easily enter the flow of fluid, reducing costly wiper trips. The spherical-like cutting structure can produce smaller plug cuttings than mills and tri-cone bits. Further, the spherical-like cutting structure can often include an effective surface cutting area of at least two times greater than similarly dimensioned tri-cone bits.

It is another object, feature, and/or advantage of the present disclosure to limit and/or remove moving parts such as ball bearings. As a result, more weight-on-bit can be applied to the bit, and the bit can operate without failure at higher revolutions per minute (RPMs). In fact, upwards of three times or greater of weight-on-bit can often be applied to an exemplary drill bit than similarly dimensioned tri-coned bits.

It is another object, feature, and/or advantage of the present disclosure to provide a drill bit with an improved profile to minimize clearance between the bit and the borehole to improve the efficiency of debris removal. The profile of an exemplary embodiment closely approximates that of a circle, which generally contours to the borehole being drilled. Further, reverse jets associated with the fluid course provide additional force to the debris opposite to the drilling direction.

These and/or other objects, features, and/or advantages of the present disclosure will be apparent to those skilled in the art. The present disclosure is not to be limited to or by these objects, features, and advantages. No single aspect need provide each and every object, feature, or advantage.

According to one aspect of the present disclosure, a subsurface drilling tool, particularly a drill bit, is provided. The drill bit includes a bit body or shank, wherein the shank comprises a pin end and an opposite cutting end. The pin end is open and comprises a fluid course extending longitudinally from the open pin end, through the shank, and through the cutting end for drilling fluid to transfer through the shank. The pin end includes a pin, screw, threads, or other means standard in the industry for attaching a drill bit to a drill stem. The cutting end comprises a plurality of ear portions configured to form the shape of a socket, wherein a ball shaped cutting tool fits inside the socket and is rotatably attached to the plurality of ear portions via an axle. The ball shaped cutting tool comprises a plurality of cones, preferably two, shaped like half-domes and placed adjacent to one another to form the ball shape. The drilling or cutting is caused by a plurality of blade inserts, preferably metal-carbide, that fit inside and protrude therefrom a plurality of holes covering the exterior of the ball shaped cutting tool, wherein each blade insert comprises a cutting face and a trailing face. The plurality of cones and, consequently, the ball shaped cutting tool may be locked in place via a locking pin through the axle. The drill bit of the present disclosure further includes a series of milling courses extending longitudinally along the outside length of the shank for milling and particles of formation to flow to the surface through the borehole.

According to another aspect of the present disclosure, a method of subsurface drilling using a drill bit includes providing a drill and a drill bit. The drill bit includes a bit body or shank, wherein the shank comprises a pin end and an opposite cutting end. The pin end is open and comprises a fluid course extending longitudinally from the open pin end, through the shank, and through the cutting end for drilling fluid to transfer through the shank. The pin end includes a pin, screw, threads, or other means standard in the industry for attaching a drill bit to a drill. The cutting end comprises a plurality of ear portions configured to form the shape of a socket, wherein a ball shaped cutting tool fits inside the socket and is rotatably attached to the plurality of ear portions via an axle. The ball shaped cutting tool comprises a plurality of cones, preferably two, shaped like half-domes and placed adjacent to one another to form the ball shape. The drilling or cutting is caused by a plurality of blade inserts, preferably metal-carbide, that fit inside and protrude therefrom a plurality of holes covering the exterior of the ball shaped cutting tool, wherein each blade insert comprises a cutting face and a trailing face. The plurality of cones and, consequently, the ball shaped cutting tool may be locked in place via a locking pin through the axle. The drill bit of the present disclosure further includes a series of milling courses extending longitudinally along the outside length of the shank for milling and particles of formation to flow to the surface through the borehole. The method subsequently involves attaching the drill bit to the drill, inserting the drill bit into the ground, and starting to drill.

According to still another aspect of the present disclosure, a drill bit configured to drill a drill bore includes a shank having a first end configured to operably connect to a drill string. Two ear portions are integrally formed to and extending from a second end of the shank. Each of the two ear portions can have an arcuate outer surface. Two rolling cutters are disposed between the two ear portions, each of the two rolling cutters having an arcuate face. A plurality of cutting elements is operably connected to each of the two rolling cutters. Each of the plurality of cutting elements has a cutting edge. The cutting edges of a portion of the plurality of cutting elements define a circle or circular configuration. The circular configuration can be further defined by the arcuate outer surfaces of the two ear portions.

The circular configuration can correspond to a circumference of the drill bore and configured to prevent backflow of drilling debris.

The drill bit can further include a plurality of protrusions extending outwardly from the shank. The plurality of protrusions can further define the circle or circular configuration. Further, the plurality of protrusions is configured to prevent wobble of the drill bit in operation. An exposed surface of each of the plurality of protrusions can be hemispherical.

According to another aspect of the present disclosure a drill bit includes a generally cylindrical bit body having a first end configured to operably connect to a drill string. Two ear portions are associated with the bit body, each of the two ear portions having a planar inner surface. An axle extends between the two ear portions. Two rotatable cutters disposed on the axle. Each of the two rotatable cutters having a planar inner surface, a planar outer surface, and an arcuate face extending between the inner surface and the outer surface. The outer surface of each of the two rotatable cutters can directly abut the inner surface of one of the two ear portions. The inner surface of each of the two rotatable cutters can directly abut one another.

The two rotatable cutters can have an on-load configuration. In the on-load configuration, a gap is disposed between the outer surface of each of the two rotatable cutters and one of the ear portions, and the inner surfaces of each of the two rotatable cutters are in contact. The on-load configuration can be associated with pulverization of rock within a drill bore. Alternatively, the two rotatable cutters can have an off-load configuration. In the off-load configuration, a gap is disposed between the inner surfaces of each of the two rotatable cutters, and the outer surface of each of the two rotatable cutters and one of the ear portions are in contact. Centripetal forces force the outer surface of each of the two rotatable cutters into contact with one of the ear portions in the off-load configuration.

According to still another aspect of the present disclosure, a drill bit is configured to drill a drill bore and includes a shank having a first end configured to operably connect to a drill string. Two ear portions are integrally formed to and extending from a second end of the shank, and an axle extends between the two ear portions. Two rolling cutters are disposed between the two ear portions and operably mounted on the axle. Each of the two rolling cutters having an arcuate cutting face between an inner surface and an outer surface.

A plurality of cutting elements can be operably connected to the arcuate cutting faces of each of the two rolling cutters, wherein the plurality of cutting elements are arranged about more than one circumference of each of the arcuate cutting faces. The plurality of cutting elements can be equally spaced. In another embodiment, each of the rolling cutters includes a plurality of ridges and a plurality of grooves in an alternating configuration, associated with the arcuate cutting face, and extending between the inner surface and the outer surface of each of the two rolling cutters. One or more notches can be disposed within the plurality of ridges. In still another embodiment, each of the two rolling cutters further comprises a plurality of three-sided cutting elements and a plurality of four-sided cutting elements associated with the arcuate cutting face.

The drill bit can further include a fluid course extending axially within the shank. The fluid course can have an inlet proximate to the first end of the shank and at least one outlet proximate to the second end of the shank. Fluid exiting the outlet of the fluid course can contact the two rolling cutters opposite a drill face of the drill bore. The fluid course can further include a bifurcated portion comprising two fluid pathways in fluid communication with the inlet. At least one outlet comprises two outlets, each of the two outlets being associated with one of the two fluid pathways of the bifurcated portion. One or more reverse jets can be within the shank and in fluid communication with the fluid course. The one or more reverse jets are configured to urge drilling debris in a direction opposite a cutting direction of the drill bit within the drill bore. The drill bit can further include a plurality of cutting elements disposed on the shank.

Different aspects may meet different objects of the disclosure. Other objectives and advantages of this disclosure will be more apparent in the following detailed description taken in conjunction with the figures. The present disclosure is not to be limited by or to these objects or aspects.

BRIEF DESCRIPTION OF DRAWINGS

Illustrated embodiments of the disclosure are described in detail below with reference to the attached figures, which are incorporated by reference herein, and where:

FIG. 1 is a perspective view of a subsurface drilling tool in accordance with an illustrative embodiment of the present disclosure;

FIG. 2 is a cross-sectional view of the subsurface drilling tool of FIG. 1 taken along section lines 2-2;

FIG. 3 is a bottom plan view of a subsurface drilling tool in accordance with an illustrative embodiment of the present disclosure;

FIG. 4A is a perspective view of a subsurface drilling tool in accordance with an illustrative embodiment of the present disclosure;

FIG. 4B is a side elevation view of a subsurface drilling tool in accordance with an illustrative embodiment of the present disclosure;

FIG. 5A is a bottom plan view of a subsurface drilling tool in accordance with an illustrative embodiment of the present disclosure;

FIG. 5B is a top plan view of a subsurface drilling tool in accordance with an illustrative embodiment of the present disclosure;

FIG. 6 is a perspective view of a cutting tool in accordance with an illustrative embodiment of the present disclosure;

FIG. 7 is a perspective view of a shank in accordance with an illustrative embodiment of the present disclosure;

FIG. 8A is a cross-sectional view of the shank of FIG. 7 taken along section lines 8A-8A;

FIG. 8B is a cross-sectional view of the shank of FIG. 7 taken along section lines 8B-8B;

FIG. 9 is a front elevation view of a cutting tool in accordance with an illustrative embodiment of the present disclosure;

FIG. 10 is a front elevation view of a cutting tool in accordance with an illustrative embodiment of the present disclosure;

FIG. 11 is a front elevation view of a cutting tool in accordance with an illustrative embodiment of the present disclosure;

FIG. 12A is a front elevation view of a cutting tool in accordance with an illustrative embodiment of the present disclosure;

FIG. 12B is a front elevation view of a cutting tool in accordance with an illustrative embodiment of the present disclosure;

FIG. 13 is a front elevation view of a cutting tool in accordance with an illustrative embodiment of the present disclosure; and

FIG. 14 is a front elevation view of a cutting tool in accordance with an illustrative embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

FIG. 1 illustrates a side elevation view of the subsurface drilling tool, particularly a drill bit, of the present disclosure. A rolling cutter, such as the one herein described, is a cutting element having at least one surface that may rotate within a cutter pocket as the cutting element contacts the drilling formation. As the cutting element contacts the formation, shearing may allow a portion of the cutting element to rotate around a cutting element axis extending through a central plane of the cutting element. The drill bit of the present disclosure includes a bit body or shank (10), wherein the shank (10) comprises a pin end (12) and an opposite cutting end (14). The shank (10) may be formed of material including, for example, metal, carbides, such as tungsten carbide, tantalum carbide, or titanium carbide, nitrides, ceramics and diamond, such as polycrystalline diamond, or a combination thereof. Also illustrated in FIG. 1, the pin end (12) has the usual threaded portion by which it may be connected to a typical drill stem (not shown), although other means standard in the industry such as pins, screws, or other means for attaching a drill bit to a drill stem may be utilized. The construction of the shank (10) may be of a conventional type well known and heretofore extensively used in rolling cutters in a conventional cross roller cutter bit.

The cutting end (14) comprises a plurality of ear portions (16), preferably two, located opposite one another on both sides of the shank (10). Moreover, the ear portions (16) extend beyond the shank (10) to assist in forming the cutting end (14) of the shank (10). For instance, the ear portions (16) are configured to form the shape of a socket (18), wherein a ball shaped cutting tool (20) fits inside the socket (18) and is rotatably attached to the plurality of ear portions (16) via an axle (24). Comprising the ball shaped cutting tool (20) is a plurality of cones (22), preferably two, shaped like half-domes and located adjacent to one another to form the ball shape as illustrated in FIG. 1. The ball shaped cutting tool (20) is thus snugly engaged and held in place by the socket (18). The drill bit of the present disclosure further includes a locking pin (38) to lock the axle (24) in place, thus, effectively locking the plurality of cones (22) into a set position.

As further illustrated in FIGS. 1 and 2, when the drill bit is rotated by the drill stem (not shown) in a borehole, the plurality of cones (22) rotate on the axle (24) and, as a very great pressure is applied by the weight of the drill stem, the plurality of cones (22) will crush the hard formation on which the drill bit is rotated. The pin end (12) of the present disclosure is open and comprises a fluid course (40) extending longitudinally from the open pin end (12), through the shank (10), and through the cutting end (14) for drilling fluid to transfer through the shank (10). The milling or particles of formation crushed by the plurality of cones (22) will be removed by the drilling fluid which is pumped in the usual manner through the open pin end (12), down through the fluid course (40) and continuing through and around the cutting end (14). The milling or particles of formation will subsequently return to the surface of the earth through the series of milling courses (36) and walls of the borehole. Thus, this process eliminates or significantly reduces “bit-balling” at this critical area of the drill bit's cutting end (14).

The arrangement of the plurality of cones (22) is such that the cones will crush substantially the entire area of the bottom of the borehole. Moreover, the plurality of cones (22) is of such composition and so manufactured as to have an extremely high compressive strength, and to be extremely resistant to transverse rupture and to abrasion. For example the plurality of cones (22) may be made of a composition of tungsten, cobalt, iron and carbon processed to produce the desired properties just referred to. The plurality of cones (22) forming the ball shaped cutting tool (20) will take the extreme loads required in drilling hard rock. No bending moment is imposed upon the hard metal of which the plurality of cones (22) is made. The plurality of cones (22) will take loads imposed upon them from any direction under operating conditions. The plurality of cones (22) forming the ball shaped cutting tool (20) eliminates sharp corners in the shank (10) from which cracks might start, thus, effectively increasing the life of the drill bit. Also, it has been found that the use of the plurality of cones (22) in forming the ball shaped cutting tool (20) not only simplifies and reduces the cost of manufacture, but also facilitates final assembly and repair of the drill bit of the present disclosure.

Illustrated in FIG. 3, the plurality of cones (22) are configured to rotate in opposite directions around the axle (24) while the drill bit is drilling or cutting through the ground, rock, or other material. The drilling or cutting is accomplished by a plurality of blade inserts (30) that fit inside a plurality of holes (28) covering the exterior of the ball shaped cutting tool (20). One blade insert of the plurality of blade inserts (30) is snugly fitted into one hole of the plurality of holes (28) and attached by means known in the industry, such as via brazing, interference fitting, welding, or threaded screws, so that the blade insert (30) does not rotate within the hole (28). Alternatively, in other embodiments, blade inserts (30) may rotate within their respective holes (28). The plurality of blade inserts (30) may have a cutting face (32) and a trailing face (34), wherein the cutting face (32) faces in the direction of blade rotation.

The plurality of blade inserts (30) according to embodiments of the present disclosure may be formed of material including, for example, metal, carbides, such as tungsten carbide, tantalum carbide, or titanium carbide, nitrides, ceramics and diamond, such as polycrystalline diamond, or a combination of substrates thereof. For instance, a carbide substrate utilized in the present disclosure may include metal carbide grains, such as tungsten carbide, supported by a matrix of a metal binder. Various binding metals may be present in the substrate, such as cobalt, nickel, iron, alloys thereof, or mixtures, thereof. In a particular embodiment, the substrate may be formed of a sintered tungsten carbide composite structure of tungsten carbide and cobalt. However, it is known that various metal carbide compositions and binders may be used in addition to tungsten carbide and cobalt. Thus, references to the use of tungsten carbide and cobalt are for illustrative purposes only, and no limitation on the type of carbide or binder use is intended. Further, diamond composites, such as diamond/silicon or diamond/carbide composites, may be used to form the plurality of blade inserts (30).

According to a further aspect of the present disclosure, a method of subsurface drilling using a drilling tool, particularly a drill bit, is provided. Illustrated in FIGS. 1-3, the method includes providing a drill and the aforementioned drill bit. For instance, the drill bit includes a bit body or shank (10), wherein the shank (10) comprises a pin end (12) and an opposite cutting end (14). The pin end (12) is open and comprises a fluid course (40) extending longitudinally from the open pin end (12), through the shank (10), and through the cutting end (14) for drilling fluid to transfer through the shank (10). The pin end (12) includes means standard in the industry for attaching the drill bit to a drill stem. The cutting end (14) comprises a plurality of ear portions (16) configured to form the shape of a socket (18), wherein a ball shaped cutting tool (20) fits inside the socket (18) and is rotatably attached to the plurality of ear portions (16) via an axle (24). The ball shaped cutting tool (20) comprises a plurality of cones (22), preferably two, shaped like half-domes and placed adjacent to one another to form the ball shape. The drilling or cutting is caused by a plurality of blade inserts (30), preferably metal-carbide, that fit inside and protrude therefrom a plurality of holes (28) covering the exterior of the ball shaped cutting tool (20), wherein each blade insert (30) comprises a cutting face (32) and a trailing face (34). The plurality of cones (22) and, consequently, the ball shaped cutting tool (20) may be locked in place via a locking pin (38) through the axle (24). The drill bit further includes a series of milling courses (36) extending longitudinally along the outside length of the shank (10) for milling and particles of formation to flow to the surface through the borehole. The method subsequently involves attaching the drill bit to the drill, inserting the drill bit into the ground, and starting to drill.

Referring to FIGS. 4A and 4B, another exemplary drill bit in accordance with the objects of the present disclosure is illustrated. Similar to exemplary embodiments previously described herein, the drill bit includes a shank (10) having a pin end (12) configured to operably connect to a drill string, and two ear portions (16) extending from a cutting end (14) of the shank (10). Two rolling cutters (22) are operably disposed between the two ear portions (16) via an axle (24). A plurality of cutting elements (30) are operably connected to the two rolling cutters (20). In the exemplary embodiment illustrated in FIGS. 4A and 4B, a plurality of depressions (42) is disposed within the shank (10) and configured to receive a plurality of protrusions (44). While FIGS. 4A and 4B illustrate depressions (42) without protrusions (44), this is primarily for illustrative purposes. In a preferred embodiment, a protrusion (44) will be operatively connected to each of the depressions (42). In an exemplary embodiment, the exposed surface of the protrusions (44) is hemispherical. The protrusions (44) can be snugly fitted into the protrusions (42) and attached by means known in the industry, such as brazing, interference fitting, welding, or threaded screws. The protrusions are configured to minimize and/or prevent wobble of the drill bit in operation, the manner in which will be discussed in detail below. Further, a plurality of cutting elements (46) can be operably connected to an angled surface (48) associated with the shank (10), as illustrated in FIG. 4B. The plurality of cutting elements (46) are configured to provide additional cutting capacity, particularly in instances where debris downstream within the drill bore falls back onto the angled surface (48) of the drill bit. For example, based on the relative diameters of the pin end (12) and the cutting end (14) of the shank (10), larger (and heavier) cutting debris being urged upwardly within the drill bore can fall back onto drill bit. As the circumference of the drill bit proximate to the cutting end (14) is generally contoured to the borehole, the larger debris can come in contact with the angled surface (48). The cutting elements (46) can further shear, crush, and/or otherwise reduce the larger debris into smaller debris such that the fluid can more easily urge the debris in a direction opposite the drilling direction. Still further, one or more reverse jet outlets (50) can be disposed within the angled surface (48). The reverse jet outlets (50) can be in fluid connection with reverse fluid passageways (96) (FIGS. 8A and 8B) and the fluid course (40). The fluid delivery system (74) will be discussed in detail below.

FIGS. 5A and 5B illustrate a bottom plan view and a top plan view, respectively, of an exemplary drill bit of the present disclosure. The figures collectively illustrate that the structures of the drill bit are arranged in and/or approximate a circle (52) or circular configuration. The circular configuration (52) of the structures corresponds to, closely contours, and/or approximates the circumference of the drill bore such that minimal clearance is between the drill bit and the drill bore. As previously expressed herein, providing minimal clearance between the drill bit and the drill bore minimizes the volume of fluid and/or debris in the area surrounding the drill bit. As a result, less pressure is required from the fluid being forced through the fluid course to urge the debris and fluid through the drill bore. Further, the circular configuration (52) of the structures minimizes wobble of the drill bit, and also maximizes the available effective cutting surface of the two rolling cutters (22).

With reference to FIG. 5A, each of the ear portions (16) includes a generally arcuate outer surface (54). The arcuate outer surface is generally contoured to the circular configuration (52). Stated differently, the radius of the arcuate outer surface (54) is approximately the same as the radius of the circular configuration (52). The arcuate outer surface (54) of each of the ear portions (16) can be truncated such that the axle (24) can extend slightly beyond the ear portions (16) but not outside the circular configuration (52).

Thus, the arcuate outer surface (54) of each of the ear portions (16) and the axle (24) collectively have an arcuate profile generally contoured to the circular configuration (52), as illustrated in FIG. 5A.

Further, each of the rolling cutters (22) includes an arcuate face (56). With reference to FIGS. 4B and 5A, the arcuate faces (56) of the rolling cutters (22) is slightly recessed from and generally contoured to the circular configuration (52). Further, the arcuate faces (56) of the rolling cutters (22) are generally contoured to the arcuate outer surfaces (54) of the ear portions (16), both when viewed from the side elevation view of FIG. 4B and the bottom plan view of FIG. 5A. The collective shape of the rolling cutters (22) and the ear portions (16) creates a generally spherical cutting tool (20) of the drill bit. More particularly, the portion of the cutting end (14) of the drill bit below an axial midline of the axle (24) is substantially hemispherical. The substantially hemispherical shape advantageously operates in three dimensions to shear, puncture, pulverize, twist and chisel both rock formation and bridge plugs in cased-well drilling. The spherical-like cutting structure can produce smaller plug cuttings than mills and tri-cone bits, and can include a larger effective surface cutting area than similarly dimensioned tri-cone bits.

With continued reference to FIG. 5A, structures in addition to the ear portions (16) are arranged in and/or approximate a circle (52) or circular configuration. In particular, the cutting elements (30) have a cutting edge (58) that generally defines the circular configuration (52). In the exemplary embodiment of FIGS. 5A and 5B, the cutting edge (58) includes the edge between the leading face (32) and the trailing face (34) of the cutting element (30). In other exemplary embodiments having alternate cutting tools (see FIGS. 10-14), the cutting edge can include the outermost surface, edge, and the like of the rolling cutters (22). The cutting edges (58) further define the circular (and/or cylindrical) configuration (52) of the cutting end (14) of the drill bit, so as to cut in three-dimensions and/or approximate the circumference of the drill bore to provide minimal clearance between the drill bit and the drill bore.

Further, the plurality of protrusions (44), also known as “wobble control,” further define the circular (and/or cylindrical) configuration (52), as illustrated in FIGS. 5A and 5B. As illustrated in FIGS. 4A and 4B, the protrusions (44) are disposed on the exterior of the shank body (10). Taken together, the drill bit, at least from the cutting end (14) to the angled surface (48) operates in a substantially cylindrical profile, particularly when rotating in operation. As a result, wobbling of the drill bit within the drill bore is minimized and/or eliminated. Further, minimal free space is between the drill bit and the drill bore to minimize backpressure of fluid and/or debris being urged in a direction opposite the cutting direction.

Still further, at least one milling course (36) is disposed on the shank body (10) in a manner to provide channels (60) for the fluid and debris to escape in a direction opposite the cutting direction. As illustrated in FIGS. 4A and 4B, the milling courses (36) extend longitudinally along an outer surface (62) of the shank body (10). Further, as illustrated in FIGS. 4A and 4B, milling courses (36) can be separated by a ridge (64), wherein protrusions (44) are disposed on the ridge (64). The milling courses (36) have a cutting face to mill the borehole and/or to urge drilling debris and fluid in a direction opposite the cutting direction with the channel (60).

Referring to FIGS. 6 and 7, each of the ear portions (16) includes a planar inner surface (66) opposite the arcuate outer surface (54). Each of the rolling cutters (22) (also referred to herein as rotatable cutters) can include an inner surface (68) opposite an outer surface (70). The arcuate face (56) of the rotatable cutters (20) extends between the inner surface (68) and the outer surface (70). In the illustrated embodiment of FIGS. 5A and 5B, the inner surface (68) and the outer surface (70) are planar.

Each of the rotatable cutters (20) includes a bore (72) through which the axle (24) is operably connected. The rotatable cutters (20) can operably be connected to the axle (24) without any intervening structures such as ball bearings, roller bearings, bushings, and the like. Based on the material selection and manufacturing of the rotatable cutters (22) and the axle (24), wear is sufficiently low such that the two metal components can be in contact. As a result, more weight-on-bit can be applied to the bit, and the bit can operate without failure at higher RPMs than similarly dimensioned tri-coned bits.

Similarly, based on the material selection and manufacturing of the rotatable cutters (20) and the ear portions (16), wear is sufficiently low such that the two metal components can be in contact. To that end, the outer surface (70) of each the rotatable cutters (22) is adjacent to, abuts, directly abuts, and/or is in contact with the inner surface (66) of the ear portions (16). Further, the inner surfaces (68) of the rotatable cutters (22) is adjacent to, abut, directly abut, and/or are in contact with one another. Taken together, the tolerances between the rotatable cutters (22) and the ear portions (16) are sufficiently small such that cutting debris is generally unable to enter a space between the outer surface (70) of the rotatable cutters (22) and inner surface (66) of the ear portions (16) and/or the inner surfaces (68) of the rotatable cutters (22).

While the tolerances between the rotatable cutters (22) and the ear portions (16) are sufficiently small, the present disclosure contemplates that relatively small gaps can exist between the same such that the rotatable cutters (22) can slide laterally on the axle (24) based on, at least in part, whether the drill bit is in use or not. More particularly, in an on-load configuration (i.e., the drill bit has weight-on-bit and spinning), centripetal and other forces can slide the rotatable cutters (22) slightly towards one another such that the inner surfaces (68) of the rotatable cutters (22) are in contact and/or direct contact. In the on-load configuration, a gap can result between the outer surface (70) of each of the two rotatable cutters (22) and the inner surface (66) of the ear portions (16). Similarly, in an off-load configuration (i.e., the drill bit has no weight-on-bit and is spinning), centripetal and other forces can slide the rotatable cutters (22) slightly away from one another such that the outer surfaces (70) of the rotatable cutters (22) are in contact and/or direct contact with the inner surface (66) of the ear portions (16). The design removes the need for washers, spacers, and/or additional components. Further, the unique design significantly improves life of the axle (24) by preventing wear from cutting debris and the like.

The drill bit can also include an improved fluid delivery system (74), as illustrated in FIGS. 7, 8A and 8B. The fluid delivery system (74) includes a fluid course (40) in fluid communication with a fluid source via an inlet (80). A portion of the fluid course (40), particularly a portion proximate to the pin end (12) of the shank (10), is similar to the fluid course (40) illustrated in FIG. 2. Referring again to FIGS. 8A and 8B, the fluid course (40) can be divided into more than one primary fluid passageways (76). In the illustrated embodiment of FIGS. 8A and 8B, the fluid course (40) is bifurcated into two primary fluid outlets (78). Of note, the shank (10) of FIGS. 8A and 8B appears hollow, but this is for illustrative purposes. In a preferred embodiment, the shank (10) is solid throughout with the passageways discussed herein comprising an absence of material. In other words, the shank (10) is comprised of bored passages within the same, as opposed to installed tube-like structures.

The primary fluid passageways (76) are in fluid communication with primary fluid outlets (78) disposed on a lower face (82) of the shank (10) between the two ear portions (16). The primary fluid outlets (78) and the lower face (82) can be considered to be on a second end (84) of the shank (10) opposite a first end, (86), wherein the first end (86) is the pin end (12). In such nomenclature, the second end (84) of the shank (10) can include the lowermost portion of the same not including the ear portions (16). The primary fluid outlets (78) on the lower face (82) are configured to provide fluid to the rolling cutters (22) on a side opposite a drill face of the drill bore. In other words, the fluid exiting the primary fluid passageways (76) (and the primary fluid outlets (78)) contact the rolling cutters (22) on a portion not in contact with the drill face of the drill bore. This can advantageously flush away any debris on the cutting elements (30) from the previous cutting iteration of the rolling cutters (22) and/or provide better lubrication for the cutting elements (30) during the next cutting iteration. Furthermore, the primary fluid outlets (78) can be offset from a first axis (88) (FIG. 5B) between the two ear portions (16). As a result, one of the primary fluid outlets (78) can provide fluid to one of the rolling cutters (22), and another one of the primary fluid outlets (78) can provide fluid to another one of the rolling cutters (22). Similarly, the primary fluid passageways (76) (and the primary fluid outlets (78)) can be offset from a second axis (90) (FIG. 5B) perpendicular to the first axis (88) and extending generally coaxial to the axle (24). In such a configuration, each of the primary fluid outlets (78) can provide the fluid to a portion of the rolling cutters (22) in the direction of rotation (i.e., a front face of the rolling cutters (22)). The design advantageously concentrates the fluid on a portion of the rolling cutters (22) about to engage the drill face of the drill bore.

The fluid delivery system (74) can further be divided into more than one secondary fluid passageways (92). As illustrated in FIGS. 8A and 8B, the secondary fluid passageways (92) can extend from the fluid course (40). The secondary fluid passageways (92) can be positioned on the fluid course (40) closer to the first end (86) and/or pin end (12) than the primary fluid passageways (76). The secondary fluid passageways (92) are associated with secondary fluid outlets (94) disposed on the lower face (82) of the shank (10). Unlike the primary fluid outlets (78), the secondary fluid outlets (94) can be positioned on the lower face (82) so as to provide fluid to portions of the rolling cutters (22) against the direction of rotation (i.e., a rear face of the rolling cutters (22)). The design advantageously concentrates the fluid in an area to rinse debris from the cutting elements (30). Further, in the illustrated embodiment of FIGS. 8A and 8B, the secondary fluid passageways (92) can be of lesser diameter than the primary fluid passageways (76).

The fluid delivery system (74) can still further include reverse fluid passageways (96). The reverse fluid passageways (96) are in fluid communication with the fluid course (40) and the reverse jet outlets (50) disposed on the angled surface (48), as illustrated in FIGS. 4B and 5B. In an exemplary embodiment, the reverse fluid passageways (96) originate on the fluid course (40) superior to the primary fluid passageways (76) and inferior to the secondary fluid passageways (92). However, alternate configurations are contemplated without deviating from the objects of the present disclosure. For example, the reverse fluid passageways (96) can originate from the primary fluid passageways (76). In the exemplary embodiment illustrated in FIGS. 8A and 8B, the reverse fluid passageways (96) generally angle upwardly and outwardly from the fluid course (40). The reverse fluid passageways (96) can intersect the secondary fluid passageways (92). Based on the positioning and orientation of the reverse fluid passageways (96), and more particular the high pressure within the same, a portion of the fluid traveling through the fluid course (40) is diverted to the reverse fluid passageways (96). The fluid is ejected through the reverse jet outlets (50) disposed on the angled surface (48). The pressurized fluid will eject generally in a direction opposite the cutting direction, whereby drilling debris and fluid contained within the drill bore will be urged in the same opposite direction. The reverse jet system is advantageous for preventing accumulation of backpressure from the cutting debris and fluid, particularly when the drill bit is oriented vertically within a drill bore.

Referring to FIG. 9, an exemplary cutting tool (98) comprised of two rotatable (or rolling) cutters (22) is illustrated. Consistent with the description of the cutting tool (20) previously expressed herein, the cutting tool (98) includes a plurality of cutting elements (30) disposed on the arcuate surface (56) of each rotatable cutter (22). The cutting elements (30) can be selectively oriented when installed on each rotatable cutter (22). For example, in the illustrated exemplary embodiment of FIG. 9, the cutting elements (30) of the right column of left rotatable cutter (22) are oriented differently than the cutting elements (30) of the left column of the right rotatable cutter (22). Further, FIG. 9 illustrates that the cutting elements (30) can be arranged about one or more circumferences (100, 102) of each of the rotatable cutters (20). The arrangement can provide for a consistent cutting profile as the rotatable cutters (20) on the axle (24) and the drill bit (and drill string) rotate as well. Still further, FIG. 9 illustrates that the cutting elements (30) can be spaced equally about the one or more circumferences (100, 102) of each of the rotatable cutters (20). More particularly, the distance between two adjacent cutting elements (30) (space ‘A’) can be the same as the space between two different adjacent cutting elements (30) (space ‘B’). Still yet further, FIG. 9 illustrates that the cutting elements (30) associated with the first circumference (100) are staggered relative to the cutting elements (30) associated with the second circumference (102). The arrangement can provide for a consistent torque profile when engaging the drill face of the drill bore.

Another exemplary cutting tool (104) includes two rotatable cutters (20) that operate as previously expressed herein, one of which is illustrated in FIG. 10. Instead of cutting elements (30) of the exemplary cutting tool (98) illustrated in FIG. 9, the cutting tool (104) has a plurality of ridges (106) and a plurality of grooves (108) disposed on the arcuate face (58) of the rotatable cutter (22). The plurality of ridges (106) and the plurality of grooves (108) can extend between the inner surface (68) and the outer surface (70) of the cutting tool (104). The plurality of ridges (106) and the plurality of grooves (108) can be arranged in an alternating configuration. Furthermore, one or more notches (110) can be disposed within the plurality of ridges (106). The notches (110) can be interior notches, or depressions that have a portion of the ridge (106) on each side. The notches (110) can also be exterior notches, or depressions proximate to the inner surface (68) and/or the outer surface (70) of the rotatable cutters (20).

Another exemplary cutting tool (112) is illustrated in FIG. 11. The exemplary embodiment of the cutting tool (112) illustrated in FIG. 11 can include a plurality of three-sided cutting elements (114) and/or a plurality of four-sided cutting elements (116) disposed on the arcuate face (58) of each rotatable cutter (22). The three-sided cutting element (114) can be similar to the four-sided cutting element (116); however, the three-sided cutting elements (114) are generally positioned adjacent to the inner surface (68) and/or the outer surface (70) of the cutting tool (112), giving it a three-sided form. The plurality of three-sided cutting elements (114) and/or a plurality of four-sided cutting elements (116) can generally be separated by troughs (118). The troughs (118) can have an arcuate lower surface as illustrated in FIG. 11. Thus, a four-sided cutting element (116) can be surrounded by four adjacent troughs (118).

Each of the three-sided cutting elements (114) and/or the four-sided cutting elements (116) can be comprised of a plurality of teeth (120, 122) separated by a groove (124). The exemplary embodiment illustrated in FIG. 11 shows one of the plurality of teeth (122) having a higher elevation than another one of the plurality of teeth (120) relative to the arcuate surface (58). The present disclosure contemplates that the shape of the three-sided cutting elements (114) and/or the four-sided cutting elements (116) about one circumference of the rotatable cutter (22) can differ from the shape of the teeth about another circumference of the rotatable cutter (22).

Referring to FIGS. 12A and 12B, still yet additional exemplary cutting tools (126 and 154) are illustrated. The exemplary embodiments illustrated in FIGS. 12A and 12B can include a plurality of platforms (128) and a plurality of floors (130) associated with the arcuate face (58) of each rotatable cutter (22). The plurality of platforms (128) and the plurality of floors (130) can extend between the inner surface (68) and the outer surface (70) of the rotatable cutters (20). The plurality of platforms (128) and the plurality of floors (130) can be arranged in an alternating configuration, as illustrated in FIGS. 12A and 12B. The plurality of platforms (128) can be wider than the plurality of floors (130).

The plurality of platforms (128) can include four generally upright sides (132). One or more of the upright sides (132) can be sloped inwardly such that the sides are trapezoidal in shape. As illustrated in FIGS. 12A and 12B, the upright sides (132) of each rotatable cutter (22) is sloped inwardly so as to form a V-shaped groove (134) between the rotatable cutters (22). Furthermore, plurality of platforms (128) can include a plurality of protrusions (136) extending outwardly from an upper surface (138) of the platforms (128). The plurality of protrusions (136) can be arranged in any configuration without deviating from the objects of the present disclosure. In the illustrated embodiment of FIG. 12A, the plurality of protrusions (136) are arranged in staggered rows. The plurality of protrusions (136) can be cylindrical-shaped, as illustrated in FIG. 12A; however, any shape can be incorporated without deviating from the objects of the present disclosure. For example, the plurality of protrusions (136) can be hemispherical, conical, cubic, diamond-shaped, and the like. For another example, the protrusions (136) can be comprised of an irregular surface area, as illustrated by the cutting tool (154) in FIG. 12B. The irregular surface can be roughened to a desired degree, to create a high friction surface for improved drilling operation.

An exemplary cutting tool (140) is illustrated in FIG. 13. Similar to the exemplary embodiments described herein, the exemplary embodiment illustrated in FIG. 13 can include a plurality of platforms (142) and a plurality of floors (144) associated with the arcuate face (58) of each rotatable cutter (22). The plurality of platforms (142) and the plurality of grooves (144) can extend between the inner surface (68) and the outer surface (70) of the cutting tool (140). The plurality of platforms (142) and the plurality of floors (144) can be arranged in an alternating configuration. Disposed within each of the plurality of floors (144) includes an aggregate (146). As illustrated in FIG. 13, the aggregate (146) is comprised of relatively small bits of metal or other similar material, which is joined through any means commonly known in the art, including but not limited to, brazing, cementing, adhesive, soldering, and the like. The aggregate (146) creates an extraordinarily rough contact surface to improve drilling operations. Further, the aggregate (146) can be joined and/or configured in any number of manners to enhance drilling properties. For example, the aggregate (146) of the embodiment illustrated in FIG. 13 is generally configured in two rows (148) at least partially separated by a ridge (150). Furthermore, the upright sides proximate to the inner surfaces (68) of each rotatable cutter (22) is sloped inwardly so as to form a V-shaped groove (152) between the rotatable cutters (22).

Certain features from the exemplary embodiments discussed herein can be selectively combined based, at least in part, on the needs of the application. For example, the cutting tool (156) illustrated in FIG. 14 is comprised of cutting elements (30) and four-sided cutting elements (116) as previously discussed.

Furthermore, the present disclosure contemplates that the two rotatable cutters (22) need not be matching counterparts. Rather, one of the rotatable cutters (22), can for example, be similar to those illustrated in FIG. 10, while another can be similar to those illustrated in FIG. 11. This provides for modularity, interchangeability, and ease of repair to minimize downtime and tailor the cutting tool precisely to the drilling operation.

The disclosure is not to be limited to the particular embodiments described herein. The subsurface drilling tool of the present disclosure and method of drilling using the subsurface drilling tool are universally applicable to drilling apparatuses of all shapes and sizes, makes, models, and manufacturers. Furthermore, while intended for large subsurface drilling operations, the drilling tool of the present disclosure may be used for drilling in all manner of uses, large and small. The foregoing description has been presented for purposes of illustration and description. It is not intended to be an exhaustive list or limit any of the disclosure to the precise forms disclosed. It is contemplated that other alternatives or exemplary aspects are considered included in the disclosure. The description is merely examples of embodiments, processes or methods of the disclosure. It is understood that other modifications, substitutions, and/or additions can be made, which are within the intended spirit and scope of the disclosure. For the foregoing, it can be seen that the disclosure accomplishes at least all that is intended.

The previous detailed description is of a small number of embodiments for implementing the disclosure and is not intended to be limiting in scope. The following claims set forth a number of the embodiments of the disclosure with greater particularity. 

What is claimed is:
 1. A drill bit configured to drill a drill bore, the drill bit comprising: a shank having a first end configured to operably connect to a drill string; two ear portions integrally formed to and extending from a second end of the shank, each of the two ear portions having an arcuate outer surface; two rolling cutters disposed between the two ear portions, each of the two rolling cutters having an arcuate face; a plurality of cutting elements operably connected to each of the two rolling cutters, each of the plurality of cutting elements having a cutting edge; and wherein the cutting edges of a portion of the plurality of cutting elements define a circular configuration.
 2. The drill bit of claim 1 wherein the circular configuration is further defined by the arcuate outer surfaces of the two ear portions.
 3. The drill bit of claim 1 further comprising: a plurality of protrusions extending outwardly from the shank, wherein the plurality of protrusions further define the circular configuration, and further wherein the plurality of protrusions is configured to prevent wobble of the drill bit in operation.
 4. The drill bit of claim 3 wherein an exposed surface of each of the plurality of protrusions is hemispherical.
 5. The drill bit of claim 4 wherein the circular configuration corresponds to a circumference of the drill bore and configured to prevent backflow of drilling debris.
 6. The drill bit of claim 1 further comprising at least one milling course extending longitudinally along an outer surface of the shank and configured to urge drilling debris in a direction opposite a cutting direction of the drill bit within the drill bore.
 7. The drill bit of claim 6 wherein the at least milling course further comprises two milling courses; wherein a portion of the plurality of protrusions is disposed on a ridge disposed between the two milling courses.
 8. A drill bit comprising: a generally cylindrical bit body having a first end configured to operably connect to a drill string; two ear portions associated with the bit body, each of the two ear portions having a planar inner surface; an axle extending between the two ear portions; two rotatable cutters disposed on the axle, each of the two rotatable cutters having a planar inner surface, a planar outer surface, and an arcuate face extending between the inner surface and the outer surface; wherein the outer surface of each of the two rotatable cutters directly abuts the inner surface of one of the two ear portions, and further wherein the inner surface of each of the two rotatable cutters directly abuts one another.
 9. The drill bit of claim 8 wherein the two rotatable cutters have an on-load configuration comprising: a gap disposed between the outer surface of each of the two rotatable cutters and one of the ear portions; and wherein the inner surfaces of each of the two rotatable cutters are in contact.
 10. The drill bit of claim 8 wherein the two rotatable cutters have an off-load configuration comprising: a gap disposed between the inner surfaces of each of the two rotatable cutters; and wherein the outer surface of each of the two rotatable cutters and one of the ear portions are in contact.
 11. The drill bit of claim 10 wherein centripetal forces force the outer surface of each of the two rotatable cutters into contact with one of the ear portions in the off-load configuration.
 12. The drill bit of claim 9 wherein the on-load configuration is associated with pulverization of rock within a drill bore.
 13. A drill bit configured to drill a drill bore, the drill bit comprising: a shank having a first end configured to operably connect to a drill string; two ear portions integrally formed to and extending from a second end of the shank; an axle extending between the two ear portions; two rolling cutters disposed between the two ear portions and operably mounted on the axle, each of the two rolling cutters having an arcuate cutting face between an inner surface and an outer surface.
 14. The drill bit of claim 13 further comprising: a plurality of cutting elements operably connected to the arcuate cutting faces of each of the two rolling cutters, wherein the plurality of cutting elements are arranged about more than one circumference of each of the arcuate cutting faces.
 15. The drill bit of claim 14 wherein the plurality of cutting elements are equally spaced about more than one circumference of each of the arcuate cutting faces.
 16. The drill bit of claim 13 wherein each of the two rolling cutters further comprises: a plurality of ridges and a plurality of grooves in an alternating configuration, associated with the arcuate cutting face, and extending between the inner surface and the outer surface of each of the two rolling cutters; and one or more notches disposed within the plurality of ridges.
 17. The drill bit of claim 13 wherein each of the two rolling cutters further comprises a plurality of three-sided cutting elements and a plurality of four-sided cutting elements associated with the arcuate cutting face.
 18. The drill bit of claim 13 further comprising: a fluid course extending axially within the shank, the fluid course having an inlet proximate to the first end of the shank and at least one outlet proximate to the second end of the shank; and wherein fluid exiting the outlet of the fluid course contacts the two rolling cutters opposite a drill face of the drill bore.
 19. The drill bit of claim 14 wherein the fluid course further comprises a bifurcated portion comprising two fluid passageways in fluid communication with the inlet, and further wherein the at least one outlet comprises two outlets, each of the two outlets associated with one of the two fluid passageways of the bifurcated portion.
 20. The drill bit of claim 14 wherein the fluid course further comprises a plurality of fluid passageways in fluid communication with the inlet, and further wherein the at least one outlet comprises a plurality of outlets, each of the plurality of outlets associated with one of the plurality of fluid passageways.
 21. The drill bit of claim 18 further comprising: one or more reverse jets within the shank and in fluid communication with the fluid course; and wherein the one or more reverse jets are configured to urge drilling debris in a direction opposite a cutting direction of the drill bit within the drill bore.
 22. The drill bit of claim 14 further comprising a plurality of protrusions extending outwardly from the shank and configured to prevent wobble of the drill bit in operation.
 23. The drill bit of claim 14 further comprising a plurality of cutting elements disposed on the shank. 